feat!: migrate Tooltip from Ariakit to Base UI

[frankieyan]

What

This is a spike to reimplement Tooltip with @base-ui/react instead of @ariakit/react.

Breaking changes

1. The ref type changed

Tooltip's ref exposed Ariakit's entire TooltipStore. It now exposes only two methods:

type TooltipHandle = { show(): void; hide(): void }

2. withArrow has been removed

This was broken in the existing implementation, so we won't be supporting it for now.

Behaviour changes

• Clicking the trigger now dismisses the tooltip (Base UI's closeOnClick) while Ariakit kept it open.
• The tooltip stays open when hovered, with a safe-polygon exit path. Ariakit closed on leaving the trigger.
• Tooltips no longer open on touch devices. Base UI's trigger is mouseOnly.
• TooltipProvider is now recommended at the app root. Without it, tooltips require the full delay when hovering from one trigger to the next.
• We documented that aria-described by was applied, but this was behaviour implemented by a previous version of Ariakit, and no longer applies in the current version